CA2315: Do not use insecure deserializer ObjectStateFormatter

Article
09/06/2023

Property	Value
Rule ID	CA2315
Title	Do not use insecure deserializer ObjectStateFormatter
Category	Security
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 9	No

Cause

A System.Web.UI.ObjectStateFormatter deserialization method was called or referenced.

Rule description

Insecure deserializers are vulnerable when deserializing untrusted data. An attacker could modify the serialized data to include unexpected types to inject objects with malicious side effects. An attack against an insecure deserializer could, for example, execute commands on the underlying operating system, communicate over the network, or delete files.

This rule finds System.Web.UI.ObjectStateFormatter deserialization method calls or references.

How to fix violations

If possible, use a secure serializer instead, and don't allow an attacker to specify an arbitrary type to deserialize. Some safer serializers include:
- System.Runtime.Serialization.DataContractSerializer
- System.Runtime.Serialization.Json.DataContractJsonSerializer
- System.Web.Script.Serialization.JavaScriptSerializer - Never use System.Web.Script.Serialization.SimpleTypeResolver. If you must use a type resolver, restrict deserialized types to an expected list.
- System.Xml.Serialization.XmlSerializer
- Newtonsoft Json.NET - Use TypeNameHandling.None. If you must use another value for TypeNameHandling, restrict deserialized types to an expected list with a custom ISerializationBinder.
- Protocol Buffers
Make the serialized data tamper-proof. After serialization, cryptographically sign the serialized data. Before deserialization, validate the cryptographic signature. Protect the cryptographic key from being disclosed and design for key rotations.

When to suppress warnings

It's safe to suppress a warning from this rule if:

You know the input is trusted. Consider that your application's trust boundary and data flows may change over time.
You've taken one of the precautions in How to fix violations.

Pseudo-code examples

Violation

using System.IO;
using System.Web.UI;

public class ExampleClass
{
    public object MyDeserialize(byte[] bytes)
    {
        ObjectStateFormatter formatter = new ObjectStateFormatter();
        return formatter.Deserialize(new MemoryStream(bytes));
    }
}

Imports System.IO
Imports System.Web.UI

Public Class ExampleClass
    Public Function MyDeserialize(bytes As Byte()) As Object
        Dim formatter As ObjectStateFormatter = New ObjectStateFormatter()
        Return formatter.Deserialize(New MemoryStream(bytes))
    End Function
End Class

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